The present invention relates to a tubular food casing based on cellulose having a coating on its inner surface which provides improved peelability properties. Also disclosed is a process for producing this casing. In a preferred embodiment, the food casing is a sausage casing.
A casing of this type is described in Brit. Pat. No. 723,323. In accordance with this printed publication, sausage casings of regenerated cellulose are provided with an internal coating composed of a water-soluble, film-forming carrier substance (starch and cellulose alkyl ether) and a high-molecular aliphatic hydrocarbon (paraffin wax, natural fats or oils), in order to more easily peel the casing from sausage mixtures having particularly strong adhesion properties (blood sausages). This known coating emulsion has the disadvantage that casings provided therewith are easily damaged during the shirring process or cannot be shirred at all. A further disadvantage is that the casing exhibits a tendency to stick to the shirring mandrel when compressed. Yet another disadvantage of this internal coating resides in the difficulty in handling hard paraffin during application to the internal surface of the sausage casing. In order to liquefy the paraffin, it must first be heated to temperatures of between 60.degree.-70.degree. C. prior to application, and then applied while hot. This procedure runs the risk of the sheathing material getting too dry and becoming brittle. Furthermore, the starch and cellulose ethers are not used as releasing agents, but merely as carrier substances, in relatively small amounts.
In order to improve the peelability of small-diameter sausage casings based on cellulose, internal coatings comprised of water soluble starch ethers and triglycerides (U.S. Pat. No. 4,248,900), cellulose ethers and cationic resins (U.S. Pat. No. 4,161,968) or cellulose ethers and castor, mineral or silicone oil (U.S. Pat. No. 3,898,348) have been described more recently.
All of these known sausage casings fall, however, under the category of "small food casings" which have diameters of between 18 and 26 mm and are used for the production and shaping of small-size skinless sausages, for example, of the Vienna type. These casings are, in general, made of cellulose tubings which are not fiber-reinforced and have relatively thin walls. The casings are also referred to as "peel-off casings" because, after stuffing these casings with a collagen-containing sausage mixture, the mixture subsequently forms its own integral sausage skin composed of the coagulated protein substances of the sausage mixture. These casings are then peeled from the integral skin of the sausage. These more recently developed internal coatings serve to facilitate the mechanical removal of the casing from the surface skin of the sausage in the production of sausages which are sold without casings, whereby the mutual adhesion between the casing and the sausage is to be reduced.
For the production of smoked, cylindrically-shaped sausages of medium or large diameter, i.e., between about 35 and 50 mm or between about 50 and 160 mm, respectively, or of smoked curved or ring-shaped sausages, smoke-permeable cellulose sausage casings which have a correspondingly larger diameter and are fiber-reinforced, or curved or ring-shaped, smoke-permeable cellulose sausage casings, so-called ring casings, are used. In general, ring casings have diameters of between about 35 and 55 mm. The composition of the sausage mixtures used for stuffing these casings is completely different from the sausage mixtures commonly used for stuffing peel-off casings, and, therefore, the adhesive forces arising between the sausage mixtures and the casings are completely different.
In the case of medium or large diameter, curved or ring-shaped sausages, such as coarse spreadable uncooked sausage, finely minced pork sausage or blood sausage, the adhesion between sausage mixture and sausage casing is markedly stronger. Using the known internal coatings for peel-off casings, it is impossible to reduce the stronger adhesive forces to a satisfactory degree. If a casing provided with an internal coating of this type is stuffed with meat, for example, coarse spreadable uncooked sausage, finely minced pork sausage or blood sausage, removal of the casing from the sausage composition is very difficult and breakage often occurs due to the insufficient releasing action towards these types of sausage meat. In comparing the coated and uncoated casings, practically no significant improvement in peelability of the coated casing is evidenced.